Method of assembling vibration dampers



May 21,- 1940.

M. TIBBETTS 2,201,932

METHOD OF ASSEMBLING VIBRATION DAMPERS Original Filed June 5, 1933 5 Sheets-Sheet 1 May 21, 1940. M TBBETTS 2,201,932

METHOD OF ASSEMBLING VIBRATIQN DMIPERS Original Filed June 5. 1933 3 Sheets-Sheet 2 May 21, 1940. Mn'BBETTs 2,201,932

METHOD OF ASSEMBLING VIBRATION DAMPERS Uriginal Filed June 5, 1953 s Sheets-Sheets v mm Patented May 21,- I940 METHOD OF ASSEMBLING VIBRATION DAMPERS Milton Tibbtts, Detroit, Mich., assignor to Packard Motor Car Company, Detroit, Mich, a corporation of Michigan Original application June 5, 1933, Serial No.

674,460. Divided and this application June 19, 1936, Serial N0. 86,201

8 Claims. (Cl. 29-84) This invention relates to vibration absorbing devices and is particularly concerned with the.

damping of vibrations occurring in motor vehicles such as result from road shock or from the of relatively thin sheets is interposed between contiguous relatively movable surfaces of the two members of the vibration absorbing device and is vulcanized to each. In order that the initial periodic impulses applied to the crankshaft of an tension of the rubber may be readily applied and internal combustion engine. It is the principal maintained one of the relatively movable memobject of the invention to improve the operation bers comprises two relatively displaceable eleof vibration dampers particularly as regards the ments, a sheet of rubber being interposed between absorption and dissipation of vibrations of small each of these elements and the other member.

amplitude and high frequency such as are de- Thus when the two elements are displaced with 19 veloped by high speeds of operation of modern respect to each other and are secured in the relainternal combustion engines and motor vehicles. tively displaced positions the tension thus ap- The present application is a division of my prior plied to the rubber is maintained independently application Serial No. 674,460, filed June 5, 1933, of the relative movement of the two members Patent No. 2,073,661. during the normal functioning of the device.

The materials composed in part or entirely of Further objects and features of the invention rubber and similar substances have found wide will be apparent from the following description employment in the field of vibration damping by taken in connection with the accompanying reason of the high mechanical hysteresis which drawings, in which:

they exhibit, such materials being characterized Figure 1 is a longitudinal sectional view of a 20 by the development of considerable heat intervibration damper for a crankshaft constructed in nally when subjected to distortion. Thus in viaccordance with the principles of the invention; bration dampers for crankshafts, rubber has been Figure 2 is a transverse section on the line 2-- 2 successfully used as the resilient element for of Figure 1; p

24' effecting the yieldable connection between the Figure 3 is a side elevation of a portion of a shaft and the relatively movable inertia member, vehicle frame illustrating the application of the the vibrations in the shaft serving to deform the invention to a vehicle suspension means or shock rubber, whereby the vibrational energy is disabsorber; sipated in the form of heat. Difiiculty has been Figure 4 is an enlarged elevational view of the 80 experienced, however, due to the failure of the shock absorber illustrated in Figure 3; rubber to respond to vibrations of small amplitude Figure 5 is a section on the line 5-5 of Figure 4; and extremely high frequency as the result of Figure 6 is a transverse sectional view of a the extreme yieldability of the rubber, the degree vehicle frame illustrating the application of the of deformation of the rubber being insufficient to invention to a motor support;

36 develop the necessary internal friction. The Figure 7 is a fragmentary sectional view taken present invention contemplates the improvement substantially on the line 1-1 of Figure 6; and of the behavior of rubber and similar materials Figure 8 is a section taken on the line 8-8 of when employed in this manner by maintaining Figure 7. the same in a state of tension, the rubber acting In order to facilitate an understanding of the more quickly and developing greater internal invention, the embodiments thereof illustrated in 40 friction when stretched. the drawings are described herein in detail. It

Thus it is a more specific object of the invenwill nevertheless be understood that no limitation tion to provide a vibration absorbing deviceemis intended by the use of specific language and ploying two relatively movable members which that such alterations of the structure disclosed are yieldably connected by an elastic deformable are contemplated as fall within the spirit and 45 means such as rubber or the like in which an scope of the invention. initial tensile or shearing stress is applied to the Referring now to Figures 1 and 2 of the drawrubber, this stress being maintained during the ings, it will be observed that the numeral I0 repnormal functioning of the device. The invention resents the crank case of an internal combustion may find employment in various types of vibraengine, having a lower .cover or oil pan II and 50 tion absorbing devices such as the conventional provided with transverse webs as shown at l2. vibration dampers for crankshafts or shock ab- The webs l2 support suitable aligned bearings l3 sorbers acting between the axles and the frame for an engine crankshaft ll, which is provided of a motor vehicle. In the preferred embodiwith the usual integral cranks l5, each crank being connected by a connecting rod 46 to a ll ments of the invention. the rubber in the form piston mounted in one of the engine cylinders. The pistons and cylinders are not shown in the drawings but are of the usual construction.

Forwardly of the first bearing i3, the crankshaft I4 is preferably formed with a reduced portion IT, on which a gear or chain sprocket l8 may be keyed or otherwise secured as indicated at 19, and used to drive the engine camshaft or other engine accessories, which are not shown in the drawings. Forwardly of the sprocket l8, the crankshaft is preferably further reduced in size as shown at 2|, and projects through a suitable opening 22 in the front wall of the crank case In. The vibration damper is illustrated as mounted at or adjacent the forward end of the crankshaft I4 and comprises a supporting portion or hub 23 keyed or otherwise rigidly secured to the crankshaft on the reduced portion thereof as indicated at 24, the hub 23 being provided with a radially disposed integral-flange 26. Surrounding the hub 23 and concentric with the crankshaft axis, is an inertia member 21 having a web portion 29 and a rim portion 28, the latter being enlarged as desired to increase the inertia effect. An annular flanged element 30 surrounds the hub 23 and is secured for rotation therewith, for

instance by the key 3| fitting in the keyway 33, it being observed that the flanged element 30 and the flange 26 of the hub 23 are spaced axially of the shaft to accommodate the web portion 29 of the inertia member therebetween, the inertia member being preferably journalled 'on the hub 23.

Annular sheets of rubber, rubberized fabric, or similarly acting material, 34 and 35 are interposed between the web portion 29 of the inertia member and the opposed contiguous faces of the flanged element 30 and the flange 26, the rubber being vulcanized or otherwise surface bonded as by cementing to these opposed faces and to the web portion 29 of the inertia member. The outer portion of the hub 23 is threaded as indicated at 31 to receive a nut 38 which engages the flanged element 30 through an interposed washer 36 to retain the element 30 against axial displacement. Under some conditions it may be desirable to thread the nut 38 on the hub 23 to an extent sufiicient to effect'some degree of compression of the rubber sheets 34 and 35 to further affect the characteristics of the rubber, it being understood, however, that the principal alteration of the characteristics of the rubber is obtained in ac cordance with the present invention by the circumferential tensioning of the rubber which may be varied to some extent by simultaneous axial compression thereof, for instance we the purpose of obtaining accurate adjustment or the tension to which the rubber is subjected to precisely control the characteristics of the damper.

In order that the desired tension may be readily applied to the rubber the following method is preferably observed in assembling the damper. The hub 23, the rubber sheets 34 and 35, the inertia member 21, and the flanged element 30 are first assembled in the manner indicated in Figure 1 of the drawings with the exception that the element 30 is so positioned on the hub that the key 3i which prevents relative rotation thereof may be inserted in the keyway 32, it being observed from Figure 2 that the two keyways 32 and 33 are spaced circumferen tially of the hub 23. The nut 38 is then threaded in position and the rubber sheets are vulcanized to the contiguous surfaces, of the inertia member and the shaft carried member. On the completion of the vulcanization the nut 38 is removed, the key is withdrawn from the keyway 32, and the flanged element 30 is rotated to an extent sufficient to permit the introduction of thekey in the keyway 33. The nut 36 is then replaced and it is apparent by reason of the rotation of the flanged member 30, the rubber sheets 34 and 35 have been placed under tension by the shearing stress applied thereto and will be maintained permanently in a condition of deformation.

The damper is thus assembled in the form of a unit which may be slid on the forward end of the, crankshaft and retained thereon against axial displacement by means of the pulley 40 which is in turn held on the shaft by the usual nut 4| which forms a coupling for engagement by the starting crank.

It will be evident that upon the occurrence of relative movement between the inertia member 21 and the shaft with its hub member 23 as the result of vibrations induced in the shaft, those portions of the rubber sheets 34 and 35 which are bonded to the hub member 23 and the flanged element 3!! will be forced to partake of movement with the shaft, whereas such portions of the rubber sheets as are united to the inertia member will partake of the movement of the latter and the rubber sheets will be considerably distorted, causing a considerable loss of energy by hysteresis or internal friction with resultant damping of vibrations. As hereinbefore pointed out, the ability of the rubber to respond to vibrations of high frequency and small amplitude is intensified to a marked extent by reason of the permanent state of tension in which it has been placed.

Referring now to the form of the invention shown in Figures 3, 4, and 5, a portion of the side frame member 45 of the vehicle adjacent the rear axle 48 is illustrated, it being understood that the rear axle may be Supported from the vehicle frame in any conventional manner to permit relative vertical movement of the axle and the frame when an irregular road bed is encountered. In order to prevent the development of synchronous movement of the frame and axle and to damp vibrations a shock absorbing device is connected between the axle and the frame. This device, as in the embodiment of the invention first described, comprises two relatively movable members and deformable elastic means such as rubber for resisting such relative movement. One of these members is secured to the frame and comprises two relatively dispiaceable elements, a substantially cup-shaped element 48 bolted to the side frame member as indicated at 49, and a hub element 50 having an annular sector-shaped flange 52 bolted to a flange 53 formed about a portion of the'circumference of the element 43, these two elements providing an annular space within which is received the annular member 55. Annuli 56 and 51 of rubber or the like are interposed between the member 55, the hub element 50, and the cup-shaped element 48 and are surface bonded to the contiguous opposed faces of these parts, for instance by vulcanization of the rubber. An arm 58 having a sector-shaped portion 59 is secured to the member 55, for instance by bolts 60, and is connected at its outer end with the axle 46, for instance by means of a bracket 62 embracing the axle housing and a plurality of bolts 8 are employed, these bolts passing through ape ures 88 spaced circumferentially of the flange 52 and through one of two sets of apertures 68 and 68 in the flange 58. In assembling the device theprocedure hereinbefore set forth with reference to the first form of the invention is substantially followed.

The cup-shaped element 48, the hub element 58, the member 55, and the rubber annuli 58, 51 are first placed in the positions shown in Figure of the drawings and the bolts 85 are inserted through the apertures 88 in the flange 52 of the hub element 58 and through the aperture 58 in the flange 53 of the cup-shaped element. The rubber is then vulcanized in position, the bolts 85 are withdrawn, and the elements 48 and 58 are rotated with respect to each other to an extent sufllcient to permit the introduction of the bolts 85 in the apertures 85 and 88, thus applying a shearing and tensile stress to the rubber annuli 58 and 51. It will be appreciated that the rubber will be maintained under tension independently of any tension which may be applied thereto as the result of assembly of the shock absorber in a vehicle; in other words, the two annuli are stretched in opposite directions and the two movable members of the device are'thus placed in a state of equilibrium with the rubber under tension independently of the vehicle load. It is in fact preferable to so assemble the shock absorber on the assembled vehicle that the tensile stress initially applied to the rubber is unchanged under normal'operating conditions.

As in the first described embodiment of the inventionthe initial deformation of the rubber alters its operating characteristics and improves its response, the device acting more quickly and being capable of dissipating a greater amount of vibrational energy than otherwise on the occurrence of relative vibratory. movement of the axle,- and frame.

It will be understood that the shock absorbing device disclosed herein may be connected between other parts of the vehicle partaking of relative movement during operation and is capable of functioning properly under all conditions in whic a conventional shock absorber might be employed, or alternatively the device may serve as a primary suspension means to yieldingly support the vehicle load in lieu of the conventional leaf spring suspension.

Referring now to Figures 6, 7 and 8 of the drawings, it will be observed that the invention is illustrated as applied to a motor support, the motor being shown as provided with laterally 7 extending arms 16 which may be formed integrally with the motor block or suitably secured thereto, these arms being carried by the side frame embers 18 of the vehicle frame. The connecti n between the arms 16 and the'side frame members is illustrated more particularly in Figures 7 and 8 of'the drawings. Thus each arm 16 may be formed adjacent its outer end to provide an annular cup-shaped portion 88. A bushing M is fitted within the cup-shaped portion 88 and is keyed or otherwise secured against rotation therein as indicated at 82. An annular sleeve 84 of rubber or similar material is secured Z by cementing or vulcanization within the bushing 8| and a bushing fitting within the sleeve 84 is likewise secured to the latter, the bushing 85 being adapted to receive a bolt 88. p

An L-shaped bracket 88 is riveted as indicated at Sl te the side frame member 18, the lower leg of this bracket overlying the lower leg of the side frame member 18 to receive a spacing member 82 therebetween. The spacing member 82 and the lower leg of the side frame member 18 are apertured to receive the bolt 88 and the lower leg of the bracket 88 is provided with a somewhat larger aperture 88- to receive the lower end of the bushing 85, a key 84 or'other non-rotative connection being provided between the bracket 88 and the bushing 85. A nut 85 is threaded on one end of the bolt 88 and a washer 88 is interposed between' the head of the bolt and the upper end of the bushing 85.

In assembling each device, the bushings 8i and 85 may be first vulcanized to the rubber sleeve 84 and are inserted in position in the cup-shaped portion 88 of the arm I8 with the key 82 in place.

The bracket 88 is then fitted on the lower end of the bushing 85 and the key 84 inserted, the keyways for the keys 82 and 84 being so disposed initially that the bracket 88 when thus assembled and prior to the application of tension to the rubber sleeve 84 lies substantially in the position in which it is shown in dotted lines*in Figure 7, preferably at approximately 90 to the final full line position. The. bracket 88 is now rotated from the dotted line to the full line position with the result that the rubber sleeve 84 is tensioned to a considerable extent. The motor and associated parts including both brackets 88 are then placed in position between the side frame member I8, the brackets 88 are bolted to the respective side frame members, the bolts'88 are inserted through the bushings 85, and the nuts 85 are tightened.

It will be appreciated that by this mode of assembly the rubber is initially tensioned, the tensile stress being applied thereto independently of the weight of the motor which is nevertheless dibeing deformed on occurrence of relative vibrational movement of the motor and the frame. This tensile stress is maintained by reason of the provision of the similar supporting devices at rectly carried on the rubber sleeves 84, the latter opposite sidesof the motor, it being apparent that the arms 18 and brackets 88 can partake of no appreciable relative rotative movement once the motor has been placed in assembled position in the frame.

By varying the initial relative displacement of the keyways for the keys 84 and 82 which. serve to connect the bushings 85 and 8| to the bracket 88 and the motor arm 18 respectively, it is obvious that the degree of tension applied to the rubber sleeve may be altered to suit the particular conditions of operation and. to obtain the maximum eifective response of the rubber to vibrational disturbances. In all three forms of the invention described herein the shearing or tensile stress initially applied to the rubber is not affected by relative movement of the elements of the device under operating conditions.

Having thus described the invention,- what is claimed as new and desired to be secured by Let-' ters Patent is:

1. A method of assembling a vibration damper for crankshafts of the type including apart fixed tothe crankshaft and a part oscillatable about the crankshaft axis, one of said parts including two elements capable of rotative displacement with respect to each other and with respect to the other of said parts, said elements having opposing faces between which the other of said parts is located and having rubber positioned between said last named part and each of said elements,

, which comprises the steps of vulcanimng the rubber to the intermediate part and to said elements,

thereafter displacing said elements with respect 7 to each other to apply tension to the rubber, and securing the elements together to maintain the rubber under tension.

2. A method of assembling a vibration absorbing device of the type comprising two relatively moving parts, one of said parts including two elements having opposing faces between which the other of said parts is located and having means composed of rubber positioned between said last named part and each of said elements, which comprises the steps of surface bonding said means to the intermediate part and to said elements, thereafter displacing the elements with respect to each other to apply tension to said means, and securing the elements together in such displaced relation to maintain said means under tension.

3. A method of assembling a vibration absorbing device of the type comprising two relatively 1 rotating parts, one of said parts including two elements having opposing faces between which the other of said parts is located and having rubber positioned between said last named part and each of said elements, which comprises the steps of vulcanizing the rubber to the intermediate part and to said elements, thereafter rotating said elements with respect to each other to apply ten- 3 moving parts having rubber positioned between them, which comprises the steps of vulcanizing the rubber to the two parts, thereafter displacing the parts relative to each other to apply tension to the rubber, and retaining the parts in such displaced position independently of the application of an otherwise unsupported load thereto. 4

6. A method of assembling a vibration absorbing device of the type including two relatively moving parts, one of said parts including two elements, and deformable elastic means actin between the other of said parts and each of said elements, which comprises the steps of surface bonding said means to each of said elements and to the other of said parts, thereafter relatively displacing said elements to apply tension to said means and securing the displaced elements together to maintain such tension.

'7. A method of assembling a vibration absorbing device of the type including two relatively moving parts, one of said parts including two elements, and deformable elastic means composed essentially of rubber acting between the other of said parts and each of said elements, which comprises the steps of vulcanizing said rubber to each of said elements and to the other of said parts, thereafter displacing said elements with respect to each other to apply tension to the rubber, and securing the elements together to maintain the rubber under tension.

8. A method of assembling a vibration damper for crankshafts of the type including two relativeiy oscillatable parts, one of said parts including two elements capable of relative ro'tative displacement with respect to each other and with respect to the other of said parts, and deformable elastic means acting between the other of said parts and each of said elements, which comprises the steps of surface bonding said means to each of said elements and to the other of said parts, thereafter relatively rotating said elements to apply tension to said means, and securing the rotated elements together against further relative rotation to maintain such tension.

MILTON TIB BETTS. 

